Assessing new, potential reduced exposure products (PREPs) for smokers is essential to predict if they will increase, decrease, or fail to change the health risks of smoking. In the past, some harm reduction efforts (i.e., low-yield cigarettes) did little to reduce smoking's lethality. Smokers using these cigarettes compensated for lower yields of nicotine by taking larger, longer, or more frequent puffs, thus potentially increasing exposure to harmful smoke constituents. In addition, some research indicates that men and women differ in their response to nicotine/tobacco; thus it is important to understand differential responses to these products. [unreadable] [unreadable] To assess the effects of PREP use, male and female smokers will participate in a 4-week, within-subjects study. Each week, participants will use either one of two PREPs, their own brand, or will abstain from smoking. Smokers will use these products outside of the laboratory but will be also be assessed for behavioral changes in the laboratory. Subjective and physiological withdrawal suppression, as well as smoke constituent exposure (CO, nicotine, nitrosamines) will be measured. Measuring these factors is essential to determine if these PREPs reduce the risk associated with smoking, and to avoid past failures to evaluate products which claimed to decrease exposure to harmful smoke constituents.